KA M4 AEG losing power every shot

MonnoncMaxou · July 22nd, 2012, 12:07

Hi,
I have a feeling this one is simple but I'm looking for second opinions. After a spring downgrade on a KA M4, I've been observing the following on chrono:

1st shot solid 330FPS
2nd 275FPS
3rd 220 FPS
4rd 170FPS
5th 120FPS
6th 97 FPS

The last shot seemed to skip. As if the gear went under the tappet plate and grabbed it on the way back.

and then the cycle restarts at 330ish and goes down again for a few shots.

I was suggested by a friend who has some experience with AEGs to replace piston o-rings.

Anyone else has an idea?

peacekeeper · July 22nd, 2012, 12:41

regrease and reshim perhaps ?

SuperHog · July 22nd, 2012, 12:49

Each time the gear box cyles, your shot to shot should slightly vary but not keep on dropping FPS unless there is something slowing it down.

A spring downgrade should not cause those problems.

The other problem that can happen, is you may have placed one too many shims from a gear to another causing binding to increase as you shoot more.

I suggest you take the gear box a part and recheck everything before you wreck your gun.

Styrak · July 22nd, 2012, 19:29

Sounds like an airseal problem. It'll have to be opened up and the cylinder head and piston head checked.

MonnoncMaxou · July 24th, 2012, 11:31

Well i reopened the gearbox, closed it up again and it worked at a solid constant FPS. I think it was an issue with the tappet plate which wasn't secured down fully by a shim.

Thanks for your help guys. It will be helpful in the future.

Styrak · July 24th, 2012, 15:27

I'm pretty sure it wasn't that, there are no shims for a tappet plate.

However you seem to have fixed your issue just by sheer luck.

ThunderCactus · July 24th, 2012, 18:26

over shimming the sector gear would cause the tappet to stick back or not open though

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July 22nd, 2012, 12:07	#1
MonnoncMaxou Trader rating Join Date: May 2012 Location: Montréal	KA M4 AEG losing power every shot Hi, I have a feeling this one is simple but I'm looking for second opinions. After a spring downgrade on a KA M4, I've been observing the following on chrono: 1st shot solid 330FPS 2nd 275FPS 3rd 220 FPS 4rd 170FPS 5th 120FPS 6th 97 FPS The last shot seemed to skip. As if the gear went under the tappet plate and grabbed it on the way back. and then the cycle restarts at 330ish and goes down again for a few shots. I was suggested by a friend who has some experience with AEGs to replace piston o-rings. Anyone else has an idea? Last edited by MonnoncMaxou; July 22nd, 2012 at 12:10..

July 22nd, 2012, 12:49	#3
SuperHog Trader rating Join Date: Jul 2011 Location: Toronto, Ontario	Each time the gear box cyles, your shot to shot should slightly vary but not keep on dropping FPS unless there is something slowing it down. A spring downgrade should not cause those problems. The other problem that can happen, is you may have placed one too many shims from a gear to another causing binding to increase as you shoot more. I suggest you take the gear box a part and recheck everything before you wreck your gun. Last edited by SuperHog; July 22nd, 2012 at 12:56..

July 22nd, 2012, 19:29	#4
Styrak Trader rating Join Date: Jan 2007 Location: Saskatoon, SK	Sounds like an airseal problem. It'll have to be opened up and the cylinder head and piston head checked. __________________ Airsoft Sales and Repair/Upgrade Services

July 22nd, 2012, 12:41	#2
peacekeeper formerly bazza Trader rating Join Date: May 2004 Location: Calgary alberta	regrease and reshim perhaps ?

July 24th, 2012, 11:31	#5
MonnoncMaxou Trader rating Join Date: May 2012 Location: Montréal	Well i reopened the gearbox, closed it up again and it worked at a solid constant FPS. I think it was an issue with the tappet plate which wasn't secured down fully by a shim. Thanks for your help guys. It will be helpful in the future.

July 24th, 2012, 15:27	#6
Styrak Trader rating Join Date: Jan 2007 Location: Saskatoon, SK	I'm pretty sure it wasn't that, there are no shims for a tappet plate. However you seem to have fixed your issue just by sheer luck. __________________ Airsoft Sales and Repair/Upgrade Services

July 24th, 2012, 18:26	#7
ThunderCactus Not Eye Safe, Pretty Boy Maximus on the field take his picture! Trader rating Join Date: Feb 2007	over shimming the sector gear would cause the tappet to stick back or not open though

KA M4 AEG losing power every shot

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